Born in Edinburgh, Scotland, Kate Cumming's family moved to Montreal, and then to the bustling cotton port of Mobile, Alabama. Early in the Civil War, Kate was inspired by an address of the Rev. Benjamin M. Miller of Mobile to volunteer to help in Confederate hospitals. Kate was also greatly influenced by the work of Florence Nightingale, having known at least two people who had served with Nigthingale during the Crimean War.

At the age of 27, in April of 1862, and against the wishes of her family, who felt that "nursing soldiers was no work for a refined lady," Kate left for Northern Mississippi in April 1862, along with forty other women. The group of women, largely untrained, arrived outside the battlefield of Shiloh, while the battle was still in progress. Most women left soon after, but Kate remained in nearby Corinth and Okalona, Mississippi until June, 1862. She then spent two months in Mobile, Alabama, but soon volunteered to work at Newsome Hospital, in Chattanooga, Tennessee. She would remain there for a year, until the summer of 1863, when the city was evacuated. During the time that Kate was at Newsome Hospital, the Confederate government officially recognized the role of women in hospitals.

From 1863 to the end of the war, Kate worked in the caravan of mobile field hospitals set up throughout Georgia to handle the effects of Sherman's devastation. The towns included Kingston, Cherokee Springs, Catoosa Springs, Tunnel Hill, Marietta, and Newnan.

Kate's work as a nurse was exemplary, but the detailed journal she kept during the War is invaluable. After the war she lived in Mobile and published A Journal of Hospital Life in the Confederate Army the War. Eight years later, in 1874, still unmarried, she moved to Birmingham, Alabama with her father. She taught school and music and became very active in chapters of the United Daughters of the Confederacy. She died in Birmingham in 1909.